1. Field of the Invention
The present invention relates to a device for detecting termination of connection to a program to be paid for, received by a subscriber unit via an interactive remote distribution network.
2. Discussion of the Background
The interactive distribution by cable of video frequency signals from a distribution center, forming the head of a star network, to subscribers each provided with a terminal connected to this cable is a technique which rests upon the transmission to the distribution center of connection requests formulated remotely by the subscribers. These requests may be managed by a microcomputer controlling a switching grid capable of establishing connections between each cable beginning and each information source available in the distribution center. The request is routed to the distribution center by the connection cable cable which connects this center to the subscriber terminal and which serves mainly to transmit to the subscriber the video signals corresponding to the program selected.
The connection of the subscriber cable to the program sources may also be made in the way described in the patent application filed by the Applicant Company on the same day as the present application and entitled: "Network for interactive distribution of video, audio and telematic information". Briefly, this alternative method consists in using, in the distribution center, a switching module for each subscriber, this module containing a multiplexer with P input tracks and one output track, and a remote control receiver intended for selecting one of the P tracks carrying the programs from the information sources. In this case, the microcomputer of the distribution center samples the modules in order to find out the connection states with a view to billing the services rendered by the distribution network and, if appropriate, it proceeds authoritatively to connection changes when the subscriber makes a choice to which he is not entitled. The subscriber's request is transmitted by the cable which connects him individually to the distribution center, and the microcomputer has available the information relating to the connection established between the subscriber cable and the information source corresponding to the choice which he has expressed. This request shares the cable with the video signals without causing interference, by virtue of the use of a carrier modulated by the coded message which represents this request. This carrier has a frequency close to the frequency standard of the video signals broadcast by the remote distribution system for feeding for example a television situated at the subscriber's home or any other electronic audio, video or telematic device capable of processing these signals.
The subscriber terminal comprises a keyboard associated with a remote control emitter and with means enabling the application to the connection cable of information in a form able to be received by the corresponding equipment of the distribution center.
Among other things, the distribution center has the task of keeping an account of access to the information sources as a function of elements such as the nature of the program selected and the duration of connection and the time slot. For this purpose, it does not suffice that a connection request be executed, because since the last request the subscriber may have ceased making use of the program which is broadcast to him. The subscriber may for example be invited to formulate a request for free connection after each phase of using a program to be paid for, but he may forget to do so, in particular when he leaves the remote distribution network in order to make use of another signal source (television programs broadcast by electromagnetic waves, personal video games, etc). The equipment intended to receive the remotely distributed signals at the subscriber's home are of standard type and do..not have means of sending back to the distribution center an operating status which the latter may take into account to avoid any incorrect billing.